The invention relates to an apparatus for detecting heat sealed places of plastic film means.
For example, in a machine for successively making plastic bags, it is frequent practice to make plastic film means include heat sealed portions each of which has a surface minutely rugged to constitute a pattern such as a mesh. The plastic film means is then fed longitudinally thereof and intermittently, and cut along a line predetermined at or near the heat sealed portion by a cutler. In this case, it is required to cut the plastic film means precisely along a line predetermined at or near the heat sealed portion thereof. Accordingly, it is desirable to detect the heat sealed place of plastic film means whenever the plastic film means is fed longitudinally thereof and intermittently. Under the circumstances, the applicant proposed a new type of apparatus for detecting the heat sealed places of plastic film means, before this application, as disclosed in Japanese Laid-Open Patent Publication No. 190,608 of 1999.
In the apparatus of the publication, a light source and an optical sensor are opposed to the plastic film means so that the light source emits light which reflects from or permeates through the plastic film means to be directed tea the optical sensor. The reflecting or permeating light is deflected by the minutely rugged surface of heat sealed portion to change the amount of light received by the optical sensor, when the heat sealed portion reaches a position at which the apparatus is disposed. As a result, there would appear a wave-shaped difference in amount of light received by the optical sensor in a direction perpendicular to the direction in which the plastic film means is fed. The optical sensor then reads out the minutely rugged surface of heat sealed portion from the wave of difference to detect the heat sealed place of the plastic film means. However, to tell the truth, the apparatus is uncertain to detect the heat sealed place to be problematic in reliability. This is considered as a matter due to the relation between the minutely rugged surface and the amount of light received by the optical sensor. Though the reflecting or permeating light is sure to be deflected by the minutely rugged surface, the deflected conditions are very complicated. It is therefore considered that the wave-shaped difference is not always brought into existence in amount of light received by the optical sensor, even if the reflecting or permeating light is deflected. In such the case, the apparatus can not read out the minutely rugged surface of heat sealed portion from the wave of difference to detect the heat sealed place of plastic film means.
It is therefore an object of the invention to reliably detect the heat sealed places of plastic film.
According to the invention, there is provided an apparatus for detecting heat sealed places of plastic film means which is fed in a direction. The plastic film means includes heat sealed portions formed at the heat sealed places. Each of the heat sealed portions has a surface minutely rugged to constitute a pattern such as a mesh. In addition, light source means and an optical sensor are opposed to the plastic film means. A cover plate is disposed between the optical sensor and the plastic film means. The cover plate includes small hole or narrow slit means through which light passes. The light source means emits light which reflects from or permeates through the plastic film means to be directed to tie optical sensor. The optical sensor image recognizes the reflecting or permeating light and reads out the minutely rugged surface of heat sealed portion to detect the heat sealed place of plastic film means in accordance with a variation of image.
It is preferable that the light source means comprises a plurality of light sources spaced from each other and opposed to the plastic film means.
It is also preferable that the light sources are spaced from each other in directions parallel and perpendicular to the direction in which the plastic film means is fed.
In addition, it is preferable that the small hole or narrow slit means comprises a plurality of small holes or narrow slits formed in the cover plate to be spaced from each other.
Furthermore, it is preferable that the small holes or narrow slits are spaced from each other in directions parallel and perpendicular to the direction in which the plastic film means is fed.
In a preferred embodiment, the plastic film means is fed longitudinally thereof and intermittently. In addition, the plastic film means is heat sealed widthwise thereof whenever intermittently fed. The optical sensor then detects the heat sealed place of plastic film means whenever the plastic film means is intermittently fed. A cutter is disposed at a position and moved by position adjustment means to adjust the position of edge of cutter in a direction parallel to the direction in which the plastic film means is fed, in response to a detecting signal transmitted from the optical sensor so that the plastic film means can be cut along a line predetermined at or near the heat sealed portion thereof by the cutter.
The plastic film may be heat sealed widthwise thereof by seal bar means disposed at a position. The optical sensor then detects the heat sealed place of plastic film means whenever the plastic film means is intermittently fed, to adjust the feed length of plastic film means or the position of heat seal bar means in response to a detecting signal transmitted from the optical sensor so that the plastic film means can be cut the line predetermined at or near tile heat sealed portion thereof by a cutter.
In other embodiment, standing pouches are made from the plastic film means. Each of the standing pouches comprises rectangular panel materials which are superposed into two layers to have bottom and opposite side edges. A bottom material is folded into halves, superposed into two layers and interposed between the layers of panel material at the bottom edges thereof. One of the layers of panel material is bottom sealed with one of the layers of bottom material to include a bottom sealed portion formed along the bottom edge of panel material. The other layer of panel material is bottom sealed with the other layer of bottom material to include a bottom sealed portion formed along the bottom edge of panel material. The layers of panel material are cross sealed with each other to include cross sealed portions formed along the opposite side edges of panel material. Each of the bottom and cross sealed portions has the minutely rugged surface. The optical sensor reads out the minutely rugged surfaces of bottom and cross sealed portions to judge whether the relation in place between the bottom and cross sealed portions is good or no good, whenever the panel and bottom materials are fed widthwise of the standing pouches and intermittently after being bottom and cross sealed in a standing pouch making process.
It is preferable that each of the bottom sealed portions includes unsealed portions formed therein. Each of the unsealed portions has a surface which is not or barely minutely rugged. In the case, the optical sensor can judge whether the relation in place between the bottom and cross sealed portions is good or no good, in accordance with the place of unsealed portion.
It is preferable that each of the bottom sealed portions has a bowl-shaped upper edge. In the case, the optical sensor can judge whether the relation in place between the bottom and cross sealed portions is good or no good, in accordance with the place of bowl-shaped upper edge.
It is preferable that punch holes are formed in the bottom material at intersections between the bottom and cross sealed portions. The layers of panel material are partially sealed with each other at the places of punch holes. The punch holes protrude from the cross sealed portions to have protruding portions formed on the opposite sides of the cross sealed portions. Each of the protruding portions has a surface which is not or barely minutely rugged. In the case, the optical sensor can judge whether the relation in place between the punch holes and the bottom and cross sealed portions is good or no good, in accordance with the place of protruding portion.
It is preferable that the cross sealed portions have center lines along which notches are formed into the cross sealed portions from the bottom edges of panel material. In the case, the optical sensor can judge whether the relation in place between the notches and the bottom and cross sealed portions is good or no good.
In other embodiment, the optical sensor reads out the minutely rugged surfaces of bottoms and cross sealed portions to judge whether the relation in place between the bottom and cross sealed portions is good or no good, when the standing pouches are fed widthwise thereof after being made.
In the embodiment, each of the bottom sealed portions may include an unsealed portion formed therein. In the case, the optical sensor can judge whether the relation in place between the bottom and cross sealed portions is good or no good, in accordance with the place of unsealed portion.
Each of the bottom sealed portions may have a bowl-shaped upper edge. In the case, the optical sensor can judge whether the relation in place between the bottom and cross sealed portions is good or no good, in accordance with the place of bowl-shaped upper edge.
Punch holes slay be formed in the bottom material at intersections between the bottom and cross sealed portions. The punch holes may protrude from the cross sealed portions to have protruding portions formed on the opposite sides of the cross sealed portions. In the case, the optical sensor can judge whether the relation in place between the punch holes and the bottom and cross sealed portions is good or no good, in accordance with the place of protruding portion.
It is preferable that each of tile standing pouches are corner cut at corners between the bottom and opposite side edges thereof to give an appearance. In the case, the optical sensor can judge whether the appearance of corner cutting is good or no good.
In other embodiment, the optical sensor reads out the minutely rugged surfaces of cross sealed portions to judge whether the sealed width of cross sealed portion is good or no good, when the standing pouches are fed widthwise thereof after being made.